1. Field of the Invention
Embodiments of the present invention relate generally to image sensors, pixels, and methods and, in specific embodiments, to a pixel having a structure allowing for charge storage and readout.
2. Related Art
Various types of image sensors and pixels are discussed in U.S. Pat. No. 7,443,437, entitled “Image Sensor with a Gated Storage Node Linked to Transfer Gate,” which issued on Oct. 28, 2008, the entire contents of which are incorporated by reference herein, and which is hereinafter referred to as the '437 patent. In particular, FIG. 2 of the '437 patent illustrates a pixel with a photodiode, a shutter gate, and a transfer gate. In that pixel, a barrier region and a storage node are implemented under the shutter gate, with the barrier region under a portion of the shutter gate adjacent to the photodiode to create a barrier, and the storage node under another portion of the shutter gate to create a potential well for storage. One of the drawbacks of such a pixel structure might be a leakage of photoelectrons into the storage node, which is very close to a buried channel depleted area of the photodiode.